The present invention relates to a treatment and system for crossing an arterial lesion in order to dilate the lesion and restore normal blood flow in the artery. Such devices and methods may be used as part of a balloon angioplasty procedure. Calcified lesions require high pressures (sometimes as high as 10-15 or even 30 atmospheres) to break the calcified plaque and push it back into the vessel wall. With such pressures comes trauma to the vessel wall which can contribute to vessel rebound, dissection, thrombus formation, and a high level of restenosis. Non-concentric calcified lesions can result in undue stress to the free wall of the vessel when exposed to high pressures.
Angioplasty balloons have been employed to treat such lesions. When inflated to high pressures, angioplasty balloons can have a specific maximum diameter to which they will expand. Generally, the opening in the vessel under a concentric lesion will typically be much smaller. As the pressure is increased to open the passage way for blood flow, the balloon will be confined to the size of the opening in the calcified lesion (before it is broken open). As the pressure builds, a tremendous amount of energy is stored in the balloon until the calcified lesion breaks or cracks. That energy is then released and results in the rapid expansion of the balloon to its maximum dimension and may stress and injure the vessel walls.
Recently, a new system and method has been contemplated for breaking up calcium deposits in, for example, arteries and veins. Such a system is described, for example in U.S. Patent Publication No. 2009/0312768, Published Dec. 17, 2009. Embodiments described therein include a catheter having balloon, such as an angioplasty balloon, at the distal end thereof arranged to be inflated with a fluid. Disposed within the balloon is a shock wave generator that may take the form of, for example, a pair of electrodes, which are coupled to a high voltage source at the proximal end of the catheter through a connector. When the balloon is placed adjacent a calcified region of a vein or artery and a high voltage pulse is applied across the electrodes, a shock wave is formed that propagates through the fluid and impinges upon the wall of the balloon and the calcified region. Repeated pulses break up the calcium without damaging surrounding soft tissue.
Arteries are sometimes totally occluded with a thrombus, plaque, fibrous plaque, and/or calcium deposits. When this condition is present, the physician must first pass a soft narrow guide wire down the artery and through the occluded area. The guide wire may be as small as 0.014 inches in diameter and usually has a soft flexible tip to help avoid penetrating the artery wall in artery corners. The angioplasty balloon is then fed down the artery on the guide wire to the desired location of the blockage. Unfortunately, many times the physician is faced with a chronic occlusion which is not passable with a guide wire. This occurs when the occlusion is so tight and solid that the soft guide wire cannot penetrate through it. Stiffer guide wires may be used in these cases, but they must be used very carefully because they can easily penetrate the artery wall when forced against the chronic total occlusion.
Guide wires have been proposed that utilize radio frequency energy to open the occlusion. Unfortunately, the heat generated by the radio frequency energy to open the occlusion is intense and can damage the walls of the artery or vessel. The radio frequency energy produces a plasma which burns anything in its path. Hence, such systems must be used carefully and must be continuously moved without pause to avoid artery or vessel damage. Moreover, such an approach requires a centering mechanism that keeps the plasma centered in the artery or vessel. Such centering is difficult to achieve, especially in the corners and bends of the arteries or veins.
Hence, there is a need for an apparatus and procedure for opening a total occlusion enough to permit a guide wire and angioplasty balloon to be fed there through. Most desirably, such an apparatus and procedure would avoid damage the artery or vessel and further be compatible with the use of the aforementioned shock wave catheter systems described above. The present invention addressed these and other issues.